Maximum Carbon Content and Maximum Equivalent Carbon

[Headache2013]

Dears;

I'm writing a Technical Specification for Valves (oil and gas industry).In the paragraph dealing with ''Chemical Restriction'', I am called to specify to Valve Manufacturers the maximum carbon content and the maximum carbon equivalent.
Would you please to let me know how to specify the maximum carbon content and Maximum Carbon Equivalent for valves.
For your information: Cleint's (Owner) ITT (invitation To Tender) doesn't specify any thing.

Regards

 

[Danlap]

Not on behalf metallurgist, but in general refer to applicable ASTM standard, the maximum carbon content is 0.23% and for carbon equivalent is 0.45% (max).

However I suggest that you should check following:
a. End user Piping specification (to determine ranges of Valve material will be supplied)
b. Whether the end user is governed by some specific institution (e.g. UOP, etc.)
c. Whether some special Heat treatment process will be applied
For example, for special service (HF Alkylation), also stipulated that the minimum carbon content should be at least 0.18%

Regards,
MR

Greenfield and Brownfield have one thing in common; Valve(s) is deemed to "run to fail" earlier shall compared to other equipments

 

[Headache2013]

Dear Muktiadi;

Thank you for your answers.
a) As you may know, generally we specify for ordinary services ASTM A105 for forged valves (small bore size) and ASTM A216 WCB for sizes 2inches and bigger.
I looked to the two ASTM specification and I found C% (max) and CE% (max) are different from the 0.23% and 0.45% you advised above.
In fact: ASTM A105 stipulates 0.35% for Carbon content and 0.47% to 0.48% for CE.
ASTM A216 stipulates: 0.25% for Carbon content and 0.5% for CE.

would you please to advise the max C% and max CE% in such case?

b) You advised in your answer (c) above to check ''Whether some special Heat treatment process will be applied ''. Would you please to give example of heat treatment that may affect Max C% and Max CE% .

FYI: no end used piping specification, nor local regulation nor specific institution.

Best Regards

 

[Danlap]

Dear Headache2013,

I will like to paraphrased my statement earlier.
First of all I am not a Metallurgist and Corrosion Engineer. So, my statement below may be arguable, however this is based on my experiences and do not represent my company best practice.
What is too low and what is too much (Carbon content, CE and other things in life) is both subjective and objective from End user perspective. Nonetheless, your summary from ASTM perspective is correct
a. For carbon steel, my Plant's pipeline only used ASTM A105N, A216 WCB / WCC OR more advanced material for all sizes. The carbon steel valve family is for general services only.
However we have found on some occasion that there were several scaling built up inside the valve, and sometimes Iron Sulfide (FeS) forming which eaten up the Carbon from inside (I will not elaborate the Chemical reaction in this forum) which are deemed due to high Carbon and CE composition in combination with specific process. Thus, we standardize that its composition MAY be as high as 0.23% C and 0.45% CE.
In regards with my company Best Practice, I do not mind to accept valve with higher C and CE (as long as it is still within ASTM standard). This valves to be installed where no scaling histories ever occured.
Please bear two things in mind:
[ul]
[li]Raw material sourcing is now originated from East (India, China, etc.), we still find inconsistent composition on seasonal basis.[/li]
[li]Some End user expect the commodity valve not necessarily to be maintained up to 20 years as long do not have external leaking history. This is a wrong perception, since some chemical reaction may happens during that period.[/li]
[/ul]

As you mention earlier, No END user Piping spec and No local regulation. CMIIW, I presume this is for Upstream Platform (with limited service condition), located somewhere NOT in North America or Western Europe area.
However, Upstream in general have more money compare to Downstream, and they have periodically maintenance (Refractory, Purging, PIG, etc.) for at least once in 5 years. So they do not have similar concern of material issues I mention earlier.
Nonetheless, all of this design and selection should come from End user or their Engineering counterpart. So, I suggest that if you are only act as supplier (to be) for a Brownfield plant. Mind as well "Will supply valve as per applicable ASTM standards" statement

b. Apology, I mixed up with some Some Alloy and SS family. However yes, I've seen this also happening in some Bulk Carbon steel valves. This is due to Thermal Cycling and Tempering processes (assuming the Raw material was correct). What's the tolerance shall the Carbon content increases? That is End user Inspection / Metallurgist to decide.

Again, I am a Valve practitioner, may not rephrase the stories correctly from Metallurgical POV, I was only assessing the End result.

Regards,
MR

Greenfield and Brownfield have one thing in common; Valve(s) is deemed to "run to fail" earlier shall compared to other equipments

 

[OGMetEngr]

I'll give you the short metallurgist answer. CE and C maximums are there for weldability. If the parts need to be field-weldable (i.e. - no post-weld heat treatment necessary) then the CE and C need to have a maximum. If not field weldable, CE and C will still be important to the guy welding it. What this maximum should be will depend on what the part will be welded to, as well as what whoever is welding it is qualified to weld. You need to contact the entity that will be welding this and find out what max. CE and C they can deal with, this is assuming you need the strength and hardenability of CE and C levels near this maximum.

If the part will not be welded at all, this is a non-issue. Regardless of welding or not, NACE MR0175 compliance needs to be considered. If NACE-compliant material is required, you need more chemical composition limits, mechanical property limits, and allowable processing routes than simply CE and C (i.e. - max hardness, specified heat treatment, <1% Ni, etc).

 

[jwhit]

Also take a look at NACE MR0103 and SP0472 though they may not be needed in your case. They increase the controls required for carbon steels above and beyond MR0175.

 

[gerhardl]

Headache2013: The posts above try to pinpoint a direct answer to your question, setting down limits in in numbers for carbon and carbon equivalent.

At the same time the answers demonstrates the typical petroleum industrys' dilemma: there are also several reasons for setting the limits (welding, different standards, different variations from producers and many others). Then there are several ways to test results and handle and react to the tests results, and several different values actual to use, varying with purpose.

As usual nobody has stated or told you why the restrictions are necessessary, or if there is any reason to do anything else than described in standards.

On the general principle 'keep it simple' I tend to agree with Muktiadi:

Check with end user if there is any prevailing standard preferred, if yes, use this standard, if not, ask (end user, other departments) if there is any objection on using the content given in a certain standard (for instanct the standards suggested above by you).

Wording: as given in standard (such and such) issue/number (xxxx revision yy, for valves type zz, and (same or different for other valves), or state in figures, stating the origin/issue for the figures as described.

Note: any deviation from a standard in a technical description complicates, and should be avoided. Maybe your data sheet is not necessary at all as long as the content is described in a standard and you are refering to the standard. The most important thing to specify,and control with QC checks,is material certificates with metal analyis and content.

Good luck!